I have the exact same problem, but I do not want to use the \chapter-command as the appendix is quite short. I want my appendix to be called 'Appendix' in the table of contents.
After going back and forth I have come up with a very, very crude fix, and that is to
first define an \appendix and declare \chapter{Appendix}, so my table of contents comes up the way I want it, then proceed to cover up the chapter with e.g a solid white box and force the content up with a negative distance.
I know this fix is quite pathetic, but I only need to do this for one document, and I think this would work exactly the way I want it.
If anyone has any better suggestions to how I can do this, please share!
I will let you know if I manage to hack something together.
